Single‐mode visible laser oscillation in Pr‐doped double‐clad structured waterproof fluoro‐aluminate glass fibre

Abstract

A Pr‐doped double‐clad structured waterproof fluoride glass fibre (Pr:DC‐WPFGF) was successfully drawn, and the laser oscillation was demonstrated. The maximum output power was measured as 251.7 mW at 639.0 nm. The Pr:DC‐WPFGF was designed to be single‐mode fibre, with 0.08 of numerical aperture and 5.2 µm of core diameter. The beam‐quality factor, M 2 , was measured and evaluated to be 1.0.